Explosion bonded electrode for electrolysis



United States Patent 3,380,907 AFiARATUS FOR THE ELECTROLYTHC REFiNlNG()F NUCLEAR METALS Joseph Gerard Wurrn, Varese, italy, assignor toEuropean Atomic Energy Con1munity-Euratom, Brussels, Belgium Filed Sept.13, 1963, Ser. No. 308,778 Claims priority, application Germany, Sept.13, 1962, E 23,520 6 Claims. (Cl. 204-247) ABSTRACT OF THE DISCLGSUREThe apparatus comprises an electrolysis vessel made of electricallyconductive metal, such as copper, and formed as a double-walledinternally cooled field concentrator intended to concentrate the energyfrom a high frequency induction coil, surrounding the apparatus, on thecathode metal. The said metal is placed in a crucible located at thebottom of the vessel and made of refractory material. The said cathodemetal and the electrolyte above it are kept in a molten state by thisenergy. The copper vessel is concentrically mounted in a reactionchamber containing an inert atmosphere. The anode is dipped in themolten salt bath above the crucible. Operating with a salt charge ofNaCl, KCl and U01 a skull of solid salt mixture is formed on the innerwall of the cooled copper vessel whereby to avoid corrosion of thevessel.

This invention relates generally to the electrolytic refining of nuclearmetals from salt melts of these metals. Nuclear metals include purelyconstructional metals such as Zr, Nb and Be as well as fissionable orfertile metals such as U, Th and Pu. They are present in the melt in theform of their halogen salts.

A special manner of refining metals consists in obtaining the metal outa solid electrode which is electrically connected as the anode andconsists of the unpurified metal. The deposit electrode is then thecathode which consists of the pure metal or is at least coatedtherewith. The salt bath acts as a normal electrolyte. Since there iselectrically no natural potential difference between the electrodes, theelectrolytic process must be set into action by an external voltagesource. The pure metal travels to the cathode and the impurities go intothe salt melt.

The invention is particularly directed to an advantageous embodiment anddevelopment of the above described type of electrolytic refining.

The refining with pure and impure electrodes applies with particularadvantage to metals such as uranium or plutonium. It can be used eitherfor producing pure uranium from the halogenated impure carbide or oxide,or for the preparation of irradiated fuel elements with the fissionproducts as impurities.

The salt melt electrolysis presents a series of operational problems.From the viewpoint of chemical technology these include protection ofthe salt melt from oxidation and absorption of moisture, protection ofthe electrolysis vessel against the corrosive attack of the melt, andthe formation of dendrites at the cathode upon deposit of the separatedmetal. From the constructional viewpoint they include heating of theelectrodes and accessibility of the apparatus.

A whole series of separate measures have been proposed for the solutionof these problems. Constant sprayin g of the melt bath with inertprotective gm is to prevent oxidation of the melt. Electrolysis vesselsof graphite are not subject to corrosion by the salt melt. Dendriteformation is got around by liquid cathodes. Heating of ice the bath byinduction saves separate heating furnaces etc. These measures have inpart been successful. It is the object of the invention to utilize them,at least in effect, as far as possible together in a refining plant.

A refinery of this type is characterized in accordance with theinvention in that the electrolysis vessel, made of electricallyconductive metal, is concentrically mounted in the reaction chamber intransformer series with an HP induction winding surrounding the reactionchamber and operated with inert gas, the vessel being formed as a doublewall, internally cooled field concentrator known per se and having aradial slot and a central bore, and in that the bore has set therein amelt crucible of refractory material projecting beyond the floor of theelectrolyte vessel to form a collar, the crucible having on the floorthereof a layer of pure nuclear metal acting as cathode and a cathodicelectrode projecting thereinto, and in that furthermore the anodicelectrode (or electrodes) is arranged in the bath zone peripherally tothe melt crucible, and in that the reaction chamber, prefer ablyconsisting of translucent material, is connected to a high vacuum pump.Through this combination of characteristics it is possible to providefor optimum conditions of operation. T hus uranium was experimentallymolten at 1200l250 C. which was nearly impossible with conventionalelectrolytic cells and with external heating.

The use of a field concentrator as electrolysis vessel makes possiblefirst of all the concentration of electrical melting energy in thecrucible zone, that is the cathode. The internal cooling of theconcentrator gives the possibility of cooling the walls of the vesselwhich are in contact with the salt melt in such a way that a salt skullis formed.

The elemination of the usual furnace with its'porous ceramic partsbrings with it furthermore the great operational advantage that theapparatus can from the beginning of the operation be completelyevacuated, so that any attack of oxygen on the melt and on the nuclearmetal is prevented. Subsequent loading of the reaction chamber withinert protective gas ensures protection during operation.

The skull provides ideal protection of the vessel from corrosion withoutdisturbing the transfer of heat energy into the bath. The melt crucibleof refractory material (for example BeO or ceramics compounded with BeO)provides a liquid electrode and constitutes at the same time a meltingand collecting basin for the separated nuclear metal. The dendriteproblem is thereby surmounted. The projecting collar of the meltcrucible cooperates with the peripheral arrangement of the anodicelectrodes to provide a mechanical separating effect on the impurities.

An embodiment of the refinery according to the invention is illustratedby way of example in the accompanying drawings, in which:

FIG. 1 is a longitudinal section of the apparatus.

FIG. 2 is a detail longitudinal section on an enlarged scale of theelectrolysis section, in particular the field concentrator.

FIG. 3 is 'a cross section of the field concentrator of FIG. 2, and

FIG. 4 is a sectional perspective view of the electrolysis sectionaccording to FIG. 2.

In FIG. 1 numeral 10 indicates the electrolysis vessel, which is at thesame time the field concentrator, 11 is the HF induction winding(connected to a 1.5 mi-lz. generator of 5 kw. yield), 12 is the coolingsystem (water) for the vessel or field concentrator, 13 the meltcrucible which contains the cathode terminal, 14 the correspondingconnecting electrode, 15 the reaction chamber consti- April 30, 1968KENSUKE ONO ET AL 3,

EXPLOSION BONDED ELECTRODE FOR ELECTROLYSIS Filed March 16, 1965 5Sheets-Sheet 2 April 30, 1968 KENSUKE 0N0 ET AL 3,380,908

EXPLOSION BONDED ELECTRODE FOR ELECTROLYSIS Filed March 16, 1965 5Sheets-Sheet April 30, 1968 KENSUKE 0 0 ET AL 3,380,908

EXPLOSION BONDED ELECTRODE FOR ELECTROLYSIS Filed March 16, 1965 5Sheets-Sheet 4 F/GQ / Iii/5 L 4s 25% f 206 N 7 I /F 2 222 //2 20 April30, 1968 KENSUKE 0N0 ET AL 3,380,908

EXPLOSION BONDED ELECTRODE FOR ELECTROLYSIS Filed March 16, 1965 5Sheets-Sheet 5 /2 16 /6 {if i 10 1",: 4; /0 9 2 f A? L20 United StatesPatent 3,380,908 EXPLOSION BONDED ELECTRODE FOR ELECTROLYSIS Kensuke Onoand Shoji Tojima, Nobeoka-shi, and Minoru lkeda, Oita-shi, Japan,assignors to Asahi Kasei Kogyo Kabushiki Kaisha, Osaka, Japan, acorporation of Japan Filed Mar. 16, 1965, Ser. No. 440,140 Claimspriority, application Japan, lHar. 23, 1964, 39/15,680; Nov. 10, 1964,39/63,159; Dec. 16, 1964, 39/70,457

Claims. (Cl. 204290) ABSTRACT OF THE DISCLOSURE An electrode forelectrolysis comprises a base of corrosion resistant metal having a thinlayer of a platinum group metal explosion bonded on one face. A currentcarrying distributor of conductive metal such as copper is explosionbonded to the opposite face of the base and is enclosed with aprotective covering of corrosion resistant metal welded to the base. Theprotective covering is spaced from the copper conductor and the spacemay be filled with a low melting point alloy. The electrode may have theform of a plurality of transverse bars connected by at least onelongitudinal connecting member.

This invention relates to an electrode for electrolysis which is made byan explosive bonding process, and more particularly to an electrolyticelectrode obtained by bonding together a platinum-group metal and acorrosionresistant metal by explosion and further attaching anelectrically conductive member to the composite plate of said bothmetals.

In this specification, a platinum-group metal means platinum, iridium,rhodium, palladium, or an alloy of any combination of these metals,while a corrosion-resistant metal means acidand alkali-proof metals suchas titanium, zirconium, tantalum, or an alloy substantially composed ofany combination of these metals.

Platinum electrodes have so far been in use for electrolysis of peroxidecompounds such as perchloric acid salts and persulphate salts and forelectrolytic reduction of organic compounds. In addition, platinumelectrodes are admitted to be available for electrolysis of alkalichlorides by the mercury method; however the fact that platinum isexpensive and hard to Work restricts the formation of platinumelectrodes, which have not therefore been put a to practical use on alarge scale. Recently, there have been made many attempts to useplatinum electrodes industrially in such a manner as coating of thesurface of a corrosion-resistant base metal with platinum so as to raisethe rate of utilization of platinum.

One of the proposed methods is the spot Welding of platinum onto thesurface of a corrosion-resistant metal, but it is difficult for themethod to perform over-all platinum coating. In addition, since platinumand the corrosion-resistant metal are bonded together through an alloyedlayer as shown in FIGURE 3 of the attached drawing, a disadvantagearises that the cladding layer may separate during electrolyticoperation just as in the case of plating. There is also the method ofthermal treatment of a platinum-group metal salt in order to depositplatinum on the surface of corrosion-resistant metal, but by thismethod, it is hard to obtain an electrode which is uniform in thicknessand applicable to electrolysis at a high current density.

Further, there was proposed a dip-plating liquor for chemicalprecipitation of a platinum-group metal; however, this method allows nosufiicient deposition of a plati- "ice num-group metal on the surface ofcorrosion-resistant metal.

Since, as described above, it is difficult to perform me chanical orchemical coating of platinum on the surface of a base metal, theemployment of electrical plating has been inevitable. However, it ishard even by the electrical plating method to obtain a composite platemade up of a corrosion-resistant metal and a platinum-group metal, bothfirmly bonded together; hence, there was proposed the process ofcarrying out a thermal treatment of the composite plate in order to fixan alloy layer composed of both metals, thus attempting to producefirmly bonded electrodes. This method allows the bonding force to becomehigher than that when the composite plate is left as plated, but it ishard for the method to make the plated composite so rigid as towithstand such mechanical works as shearing and bending, and thus thisprocess lays down a restriction on the formation of electrodes and alsohas the disadvantage of the occurrence of separation of the alloy layerdue to the difference of heat generation and that of hardness.Furthermore, it is difficult for the platinum plating method to increasethe thickness of the platinum layer over several microns. In this methodthe surface of the layer usually becomes rough; hence, it is necessaryto repeat plating in order to obtain the thickness which the electrodeis required to have (2 to 20 microns).

First noted as a method to remove the above-mentioned defects is theprocess of coating a platinum-group metal on a corrosion-resistant metalby the explosive bonding method. According to this process, the strongexplosive pressure serves to bond both metals together so as to form awavy interface as shown in FIG. 4 attached to this specification;therefore, the composite plate for electrolysis thus obtained has suchadvantages as being free from any separation to each element and capableof withstanding mechanical works, and further small in electricresistance because both metals are bonded together through no such alloylayer as is formed in the cases of the plating thermal treating process,the spot welding, and so on (as shown in FIG. 3).

Nevertheless, the conventional explosive bonding process has thedrawback that, unless the layer of a platinumgroup metal is at least 25microns or more, preferably above microns, in thickness, explosivebonding itself cannot be put into practice; while the sufficientthickness of a platinum-group metal layer for an electrode is about 10microns at most, and the thickness above this is too costly and toodisadvantageous to use industrially.

The present inventors have made studies to make possible the explosivebonding of an extremely thin layer of pltainum-group metal with athickness below 100 microns onto a surface of a corrosion-resistantmetal, and have solved the problem by attaching a platinum-group metalto a suitable supporting plate and thereafter bonding by explosion theplatinum-group metal to a corrosion-resistant metal arranged to face theformer. The details of the process are to be referred to thespecification of the copending application Ser. No. 436,544, filed Mar.2, 1965.

As a commercially available electrode to be put to practical use, thecomposite plate for electrolysis thus obtained is required to undergofurther inquiry in the respect that a corrosion-resistant base metal islow in electric conductivity (for example, the electric specificresistance of titanium and that of zirconium being 55 micro-ohmsand 47micro-ohms respectively, about 30 times that of copper, which is 1.7micro-ohms and high in price.

Namely, while, in order to put a platinum-clad electrode to commerciallyadvantageous use, it is necessary to perform electrolytic operation atsuch a high current density as 50 to 200 amperes per square decimeter,the corrosion-resistant metal as an electric conductor is required tohave a cross-section which is 30 times that of copper. This fact notonly makes the operation inconvenient but also makes the use of thecomposite plate extremely uneconomical because the corrosion-resistantmetal is expensive. Moreover, a device to obtain a uniform currentdistribution must be taken into account.

Accordingly, an object of this invention is to provide an electrode forelectrolysis which is good in electric conductivity and allows a uniformcurrent distribution.

Another object of this invention is to provide an electrode which issmall in volume and capable of accepting a great current without anytrouble.

A still other object of this invention is to provide a modification ofthe electrode that meets the above-described objects.

Other objects of this invention will be apparent from the descriptionbelow.

The present inventors found that the above-mentioned objects can beattained by the procedure which comprises the explosive bonding of athin layer of a platinum-group metal which is below 25 microns inthickness onto a corrosion-resistant base metal by the method of theco-pending application Ser. No. 436,544, then the explosive bonding ofan explosively bondable and highly conductive metal to the surface ofthe corrosion-resistant metal of the composite plate formed by the firstexplosive bonding, and the covering of the highly conductive metal witha corrosion resistant metal. As the explosively bondable and highlyconductive metals are mentioned copper, iron, aluminum, silver, nickel,chromium, or an alloy of any combination of these metals.

The present invention will be further explained hereunder in connectionwith the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of an assembly in which a sheet of aplatinum-group metal is to be bonded by explosion to a plate of acorrosion-resistant metal;

FIG. 2 is a cross-sectional view of an assembly in which a metal plateplated with a layer of a platinum-group \metal is to be bonded byexplosion onto a plate of a corrosion-resistant metal;

FIG. 3 is a cross-sectional schematic depiction of a composite metalplate obtained by the thermal treatment of a corrosion-resistant metalplated with a platinum-group [metal or by the spot welding of bothmetals;

FIG. 4 represents a cross-sectional schematic view of a part of acomposite plate formed by the explosive bonding process;

FIG. 5 is an angular perspective view partly in section of a verticaltype electrode which is an example of electrodes embodying the presentinvention;

FIG. 6 is a cross-sectional view of the electrode taken on the line 1-1of FIGURE 5;

FIG. 7 is a cross-sectional view of the electrodes taken on the lineH-II of FIGURE 5;

FIG. 8 is an angular perspective view of another example with a part cutoff;

FIG. 9 is an angular perspective view of another example;

FIG. 10 shows a cross-sectional view of the electrode taken on the lineIII-III of FIGURE 9;

FIG. 11 is an angular perspective view of another exemplary electrode;

FIG. 12 is an angular perspective view of a horizontaltype electrode;and

FIG. 13 is a side view in vertical section taken on the line IV-IV ofFIG. 12, showing the central portion which includes the conductor fixedto the electrode.

The reference numerals, common among the figures, indicate thefollowing:

1 A thin cladding layer of a platinum-group metal 2 A plate of acorrosion-resistant metal 3 A binder to adhere the layer 1 to asupporting plate 4 4 A supporting plate 5 Support to holda space betweenthe sheets 1 and *2 6 A detonating explosive 7 A detonator 7' Electricwires 8 Afoundation 9 An alloy layer 10 An electrically conductive plateof a highly electricale 1y conductivemetal The edges of the electricconductive plate 10" A plate '(of a corrosion-resistant metal) coveringthe conductive plate The edges of the cover plate 11 A plate (of acorrosion-resistant metal) covering the conductive plate An electricconductor (e.g. a copper bar) A cylinder of a corrosion-resistant metalcovering the conductor 13 15 A space or clearance 16 An alloy low inmelting point (e.g. solder) 17 The base portion of the conductive plate10 18 A terminal 19 Welded portion 20 A wavy interface formed byexplosive bonding A plate of a corrosion-resistant metal The process forexplosive bonding of a thin plate of a platinum-group metal in thepresent invention is, for instance, as follows:

As shown in FIG. 1, a thin sheet of platinum-group metal 1 is stuck to asupporting plate 4, for example an iron plate 1.5 mm. of thickness, bymeans of a binder 3, and then the thin layer of the platinum-group metalis held by supports 5 so as to face a plate of a corrosionresistant basemetal such as titanium, zirconium, or tantalum (hereunder referred to asa base metal) with a spacing distance d of about one millimeter. Next,almost all of the surface of the supporting plate 4 is covered withplate-shaped explosive 6 or powdery explosive, which is thereafterinitiated by means of a detonator 7 attached to one side of theexplosive and connected to electric wires 7. The detonation propels thethin layer of the platinumgroup metal 1 toward the surface of the basemetal 2 and firmly bonds both metal sheets 1 and 2 together. Thus, anelectrode composite composed of the base metal firmly clad with a smooththin layer of the platinumgroup metal is obtained.

Instead of attaching the thin layer of the platinum-group metal 1 to thesupporting plate 4 by the above-mentioned means, this bonding processmay employ the plating of the supporting plate 4 with the platinum-groupmetal by making use of the fact that a platinum-group metal deposited byplating is characterized by being weak in bonding force and thus easilyseparable. Namely, as shown in FIG. 2, it may also be possible to platethe surface of the metallic supporting plate 4 or a non-metallic platewith a thin layer of the platinum-group metal 1 and then to initiate theexplosive just as described above so that the thin layer deposited byplating is shifted to the surface of the base metal 2 and bonded firmlyonto said surface.

In the composite plate, or electrode plate, obtained by such a processas described above, the boundary surfaces of both metals, for example,platinum and titanium, bonded together by the strong explosive pressureare firmly interlocked so as to form a wavy interface 20 as shown inFIG. 4, unlike those combined by platingannealing as seen in FIG. 3, andtherefore the composite plate formed by the explosive bonding processhas the following characteristics:

(1) Even such a metal as titanium which, when placed in the air,immediately forms the oxide film that prevents the cladding metal frombeing firmly bonded to the base metal, is easily bendable, and thebonded composite is strong in bonding force and hard to separate. If apartial ductive member in this invention will be explained inconnection, for example, with a vertical-type electrode. On the plate ofthe corrosion-resistant metal of the electrode plate obtained asdescribed above is placed, as shown in FIG. 5 to FIG. 7, a forklikeplate of a metal 10 which is high in electric conductivity, and adet-onating explosive is mounted on the conductive plate 10substantially along the center lines; then the explosive is initiated bymeans of a detonator attached to one end of the explosive. Following thedetonation, the conductive plate 10 of the metal high in electricconductivity is perfectly bonded to the base metal 2 constituting theelectrode plate by the explosive pressure so that both plates are almostcomplete with each other with a Wavy interface 20. (As to this explosivebonding process, refer to the copending application Ser. No. 346,019,and now US. Patent No. 3,344,510.) Said conductive plate 10 is connectedto a terminal 18 and covered with a plate 11 of a corrosion resistantmetal which is formed in a semicircular conduit, and the cover plate 11is welded to the base metal 2 constituting the electrode plate along thecontact line, the Weld being indicated by the numeral 19. Thus, theconductive member covered with the plate of the corrosion-resistantmetal is formed.

It is to be noted that the configuration of the conductive plate 10consisting of a metal high in electric conductivity and the arrangementof said plate 10 on the base metal 2 can be determined at will accordingto the purpose of use of the electrode. For example, a reticulate,riblike, or leaffibrous arrangement may also be employed. In the caseWhere the arrangement of the conductive member or plate is complicated,it is recommendable to cover the whole surface of the electrode platewith a plate of a corrosion-resistant metal as shown in FIG. 8.

In a case where the conductive plate alone does not provide thecross-section necessary for the specified current, it is possible topack the space 15 (shown in FIG. 6) between the cover plate 11 of thecorrosion-resistant metal and the conductive plate 10 with an alloy lowin melting point 16, such as solder, as seen in FIG. 7. In this case,the alloy low in melting point 16 is designed so as not to be attachedto the cover plate 11 of the corrosion-resistant metal but to be firmlybonded to the conductive plate 10, so that the low-melting-point alloy16 also acts as a conductor. The space 15 can be used as a passage forcooling water or heating water as well, and therefore allows theconductive plate 10 to have a sufficient thickness to contribute to theimprovement of the current efiiciency.

As seen in FIGS. 5 and 7, some portions of the conductive member, suchas a, b, and c, are provided on the surface of the base metal 2 atsubstantially the same intervals, and these portions are assembled atthe base portion 17 so that the current fed through the terminal 18 isdistributed uniformly over the electrode plate, and thus an efficientand uniform electrolysis is performable.

FIGS. 9 to 13 show three exemplary electrodes each formed with aplurality of electrodes arranged separately. In the case of separatearrangement of many electrode plates, direct bonding of a conductiveplate 10 made of a metal which is high in electric conductivity ontobasemetal plates 2 constituting the electrode plates is not conformableto the objects of this invention in respect of corrosion-resistability;therefore, it is necessary to provide a plate of a corrosion-resistantmetal between the base-metal plates 2 and the conductive plate 10. Thisis explained in connection with FIGS. 9 and 10. Five (generally anadequate number of) rectangular electrode plates, A, B, C, D and E eachcomposed of a plate of a corrosion-resistant base metal 2 explosivelycladded, on one surface, Within a thin layer of a platinum-group metal1, are placed in parallel with one another at suitable intervals S. Onthe plates of the corrosion-resistant base metal 2 is further mounted atright angles a rectangular metallic plate 22 formed ofcorrosion-resistant metal, which is then explosively bonded to thebase-metal plates 2 as in the preceding example. Next, a narrowconductive plate 10 made of a metal high in electric conductivity isplaced on the rectangular plate 22 and bonded thereto by explosion as inthe foregoing examples; thus the electrode plates A, B, C, D and E areconnected together.

The electrode shown in FIG. 11 is similar to that of the precedingexample, but the conductive plate 10 has a cross-section in the shape ofthe letter U, with both of the upright portions represented by thenumeral 10'. Namely, three (generally an adequate number of) rectangularelectrode plates, A, B, and C, each composed of a plate of acorrosion-resistant base metal 2 explosively bonded, on one surface,with a platinum-group metal are arranged in parallel with one another atappropriate intervals S. On the plates of the base metal 2 is placed atright angles a rectangular metallic plate 22 formed of acorrosionresistant metal, which is then explosively bonded to the basemetal as indicated by the numeral 20. On the metallic plate 22 isfurther placed the bottom surface of a conductive plate 10 of a metalhigh in electric conductivity and having a U-shaped cross-section, whichis thereafter bonded by explosion as indicated also by 20, with theunbonded marginal portions 10 directed vertically. The metallic plate 22and the conductive plate 10 thus bonded together are covered with aplate 11 having a U-shaped cross-section, and the edges 11 of the coverplate 11 are welded to the surface of the base metal of each electrodeplate.

In this way, the electrode plates A, B, C are fixed at the intervals Sby the conductive plate 10 and the cover plate 11 both being common toall of the electrode plates, and thus the current fed through theconductive plate 10 is distributed uniformly. The space 15 defined bythe conductive plate 10 and the cover plate 11 may be packed with ametal which is low in melting point or serve as a passage for coolingwater or hot water just as in the first example.

FIGS. 12 and 13 show an exemplary horizontal-type electrode embodyingthe present invention, and FIG. 13 is a side view in vertical sectiontaken on the line lV-IV, showing the conductor portion of the electrode.A large number of rectangular electrode plates, A, B, C, D each formedby explosive bonding of a thin sheet of a platinum-group metal 1 onto aplate of a corrosionresistant metal 2, are arranged, base-metal-side up,in parallel with one another at equal intervals S. On the surfaces ofthe plates of the base metal 2, which are on the side opposite to thelayers of the platinum-group metal, are placed at right angles twooblong metallic plates 22 formed of a corrosion-resistant metal, whichare then explosively bonded to the base metal, thereby fixing theelectrode plates. Further, the surfaces of the metallic plates 22 areexplosively cladded with conductive plates 10 made of a metal which ishigh in electric conductivity. The conductive plates 10 are then coveredwith plates 11 made of a corrosion-resistant metal and containing analloy low in melting point 16, and firmly welded to the base metal 2 atthe edges 11 in contact with the base metal 2. Between the central spotsof the two cover plates 11 fixed in parallel with each other as shown inFIG. 12 is spanned a cover plate 12 made of a corrosion-resistant metaland packed with an alloy having a low melting point 15 just as the coverplates 11 are done. The cover plate 12. is fixed to the cover plates 11so that the alloy low in melting point contained in the former and thatin the latter plates are connected together. Onto the central portion ofthe cover plate 12 is fixed a cover cylinder 14 formed of acorrosion-resistant metal, and a conductor 13 like a copper bar is putinto the cover cylinder 14 and fixed by an alloy with a low meltingpoint 16 which is packed in the cylinder 14 and in close contact withthe conductor 13. This conductor is connected to a terminal.

The rectangular electrode plate of this horizontal-type electrode, madeby explosive bonding, has the advantage that said plate can be worked tohave an adequate shape, and the cross-section may have any of suchvarious forms as the letters V, U, L, and a semicircle, which may beselectively employed according to the conditions and object of the useof the electrode plate. A composite plate made by a usual platingprocess can not be worked to have any of such shapes as mentioned above,because the work causes separation of the composite plate, thus makingthe use of the composite impossible; while the electrode of thisinvention, which is made by explosive bonding, has no such disadvantageand can be put to very effective use.

As evident from the foregoing description, this invention provides anelectrode body by explosively bonding a thin sheet or layer of aplatinum-group metal onto a surface of a corrosion-resistant base metalplate and further explosively bonding onto the other surface aconductive plate made of a metal which is high in electric conductivity,and thus has an advantage as the cost of production of the electrode canbe far lower than that of any prior platinum electrode. In addition, theelectrode plate and the conductive plate of copper or the like bondedtogether by explosion have the surfaces attached to each other firmlyand completely in a wavy form, and therefore the electrode is extremelystout and allows the smooth flow and uniform distribution of electriccurrent. Furthermore, as occasions demand, the electrode, which is aheatgenerating source in the case of high-oxidation electrolysis, can beso constructed as to be directly cooled to have a high efiiciency.Therefore, the industrial utility value of this invention is remarkablygreat.

What we claim is:

1. An electrode for electrolysis comprising a base of corrosionresistant metal having first and second faces, a thin layer of aplatinum-group metal explosion bonded to said first face of said base,current carrying means comprising highly electric conductive metalexplosion bonded to said second face of the base and a protectivecovering of corrosion resistant material enclosing said current carryingmeans and bonded to said base.

2. An electrode according to claim 1, in which said current carryingmeans comprises a stem portion and a plurality of branches separatelyenclosed by said protective covering.

3. An electrode according to claim 1, in which said protective coveringis spaced from said current carrying means to provide a space betweensaid current carrying means and said protective covering.

4. An electrode according to claim 3, in which said space between saidcurrent carrying means and said protective cover is filled withelectrically conductive low melting point metal.

5. An electrode according to claim 1, in which said layer of aplatinum-group metal has a uniform thickness less than microns.

6. An electrode according to claim 5, in whichsaid layer ofplatinum-group metal has a uniform thickness less than 25 microns.

7. An electrode according to claim 1, in which said base comprises aplurality of transverse member and at least one connecting membercrossing and explosion bonded to said transverse members.

8. An electrode according to claim 7, in which said current carryingmeans comprises a conductor extending along and explosion bonded to saidconnecting member.

9. An electrode according to claim 7, in which said base comprises aplurality of spaced transverse members and a plurality of connectingmembers crossing and explosion bonded to said transverse members, and inwhich said current carrying means comprises conductors extending alongand explosion bonded to said connecting members.

10. An electrode according to claim 9, in which said current carryingmeans comprises conducting means connecting said conductors and saidprotecting covering encloses said conducting means.

References Cited UNITED STATES PATENTS 2,434,731 1/ 1948 Zu Eltz 2042863,060,879 10/1962 Staba.

3,140,539 7/ 1964 Holtzman.

3,271,289 9/1966 Messner 204286 XR 3,291,714 12/1966 Hall et al.

3,292,253 12/ 1966 Rossner et al. 72-56 FOREIGN PATENTS 616,029 3/1961Canada.

HOWARD S. WILLIAMS, Primary Examiner.

D. R. JORDAN, Assistant Examiner.

